One of the things that we have found helpful as a family is to have a regular time of family worship in which we spend time reading the Bible, praying, singing a hymn, memorizing catechism, and memorizing Bible verses.
Our children are 8, 5, 4, 20 months, and 12 days. The Bible that we read from is Catherine Vos's Story Bible and it is the most complete children's story Bible that we have ever read. For Bible memory and catechism we use Truth and Grace memory books published by Founders Press. It is designed for age 2 through 12th grade. These booklets are amazing! They have a format all set up for you with age appropriate verse memory, catechism, and hymns. As for the hymns, we use the Celebration Hymnal (since it is the hymn book used by our church). We memorize the hymns (not the choruses). We focus on singing one hymn a week.
On a later post I will also share some doctrine books that have been helpful to us that we have read to our children on Sundays.